This career enhancement application will facilitate the training of an established engineering research faculty member in the area of stem cell research, particularly associated with response of human embryonic stem cells to the mechanical properties of their surroundings and mechanical forces to which they are subjected. It is hypothesized that both the mechanical response produced in the surrounding matrix by action of the cell and the mechanotransduction events that this interaction initiates, and the action of external forces applied to the cell via its surrounding matrix and the mechanotransduction events that these applied forces elicit will influence differentiation. The long term goal is to simultaneously study, in real time, the differentiation of stem cells and the mechanics of their surrounding environment. The objective of the applicant's research is to control the differentiation of human embryonic stem cells encapsulated within a 3D hydrogel matrix through modification of the hydrogel material properties and the use of mechanical stimulation. The specific target of this research is stem cell development toward cardiac cell lineages including multipotent cardiovascular progenitors and cardiomyocytes. To be highly effective both as a researcher, collaborator, and mentor in the stem cell field, the applicant needs background knowledge of stem cells, developmental biology, and research characterization techniques. The environment in which the applicant works is exceptionally well suited for both training and research in human embryonic stem cells. The candidate will have access to internationally renowned researchers, cutting edge courses, and superb facilities at the University of Wisconsin - Madison and the WiCell Research Institute. Heart disease is a significant national health issue in the U.S. and in developed countries it is the leading cause of death. One of the key reasons that this disease is so challenging to treat is that heart muscle cells do not proliferate and thus damage created by myocardial infarction is not directly reversible. Human embryonic stem cells show significant promise for the treatment of heart disease and this research can be extended by the use of hydrogel systems that influence differentiation and may ultimately be used in tissue engineering for cardiac repair or to address other diseases and injuries.